Angiogenesis is a physiologic process in which new blood vessels are formed to meet the oxygen demands of local tissues. With the identification of specific biologic mediators of angiogenesis, it is now possible to consider "therapeutic angiogenesis" where angiogenic molecules could be administered to develop new vascular networks to circumvent the ischemic consequences of atherosclerosis occluding the arterial system. The focus of this application is to evaluate the hypothesis related to the biology of the in vivo delivery of the potent angiogenesis-mediator, vascular endothelial growth factor (VEGF) in the form of a cDNA using replication deficient recombinant adenovirus (Ad) vectors. The VEGF gene is naturally expressed through alternative splicing as four mRNA transcripts, coding for secreted proteins of 206, 189, 165 and 121 residues, each with different bio availability secondary to different associations with the extracellular matrix. The VEGF proteins exert their function almost exclusively on endothelial cells through two specific receptors, flt-1 and KDR/flk-1. In order to develop a gene therapy study using Ad vector-mediated transfer of the VEGF-related genes for the treatment of diffuse atherosclerosis, the specific aims of this application are focused upon: (i) the characterization of the angiogenic response of the different VEGF isoforms delivered with Ad vectors, (ii) the evaluation of the consequences of providing VEGF to tissues after Ad vectors have been used to transfer the cDNAs for the VEGF receptors to the endothelium and (iii) to examine whether modification of the genotype of the Ad capsid, deletion of the E4 gene or the addition of the E3 gene will escape anti-Ad vector recognition by neutralizing antibodies and/or cellular immunity, thus permitting repetitive Ad vector-mediated VEGF or VEGF receptor gene transfer and expression in order to evoke localized angiogenesis as needed. The results of these studies should help define gene therapy strategies for therapeutic angiogenesis for the treatment of atherosclerosis.